I have a son who is about to turn two. He still wears diapers. Pampers Cruisers with Dry-Max, to be precise. Over the past 4 months or so, he’s been fighting this chronic bum rash (WARNING: for those who don’t have kids, graphic bum and diaper discussion ahead). His bum would often be red and inflamed, with what looked like patches of hot-water scolding. Especially around the, um… hole. The poor little guy would wince and squirm in pain when we changed his diaper.

We took him to the doctor and our MD told us that it was probably an infection and gave us a prescription cream. It seemed to help, sort of. We’d put it on him a couple times a day. But, two small jars of cream later, we’re still battling this rash.

Turns out we’re not the only ones. Many families are coming forward with similar stories. And what’s the common thread? They are all using Pampers Cruisers with Dry-Max, and their kids have diaper rashes. The complaints have congealed into a full-fledged FaceBook lobby asking Pampers to get rid of this new line of diapers, and bring back the previous model.

As a parent of a child who is suffering, I am compelled to find a solution, and blaming Pampers seems like an easy road to take. However, I’m also a scientist and I’m aware of the psychological pitfalls that can lead one to false conclusions.

Here’s the problem. Hundreds of thousands of babies battle diaper rashes every day. Also, hundreds of thousands of babies wear Pampers Cruisers with Dry-Max every day. Statistically, it’s a slam-dunk that thousands of babies wearing those particular diapers will also develop a diaper rash. That is, even if the type of diaper has absolutely nothing to do with one’s chances of getting a diaper rash, we would see thousands of cases of Pampers Cruisers babies with rashes. With the Internet, it’s simple for these parents to run into each other, and start noticing a pattern.

Here is another pattern that I’ve noticed. Children with bigger feet are better at reading. Of course, this is the canonical example used to illustrate the difference between correlation and causation. If two events occur together more frequently than would be expected by chance, we say they are correlated. One thing that can generate correlation is causation; one event causes the other event to occur. In our reading example, we would be wrong to conclude that bigger feet cause children to read better. Rather, foot size and reading ability are correlated because they both occur as kids grow and go to school.

So, do Pampers diapers cause bum rash? The problem is that no one has even established that there is a correlation between the diapers and rashes, much less a causal link. It’s not clear that using Pampers with Dry-Max increases a baby’s chance of getting a wicked rash. The fact that we see an army of parents calling for action is quite likely due to the fact that Pampers is such a popular brand. Many parents erroneously leap to the false conclusion that the diapers are causing the rash. Some of those parents are vocal. And once a few start spreading the word, the rumour can go viral.

In a statement released by Proctor & Gample (the company that owns the Pampers brand), Jodi Allen (Pampers VP) said that their product has been thoroughly tested, and that they “have found no evidence whatsoever that the reported conditions were in any way caused by materials in our product.” They have shared their findings with the CPSC, and “welcome its involvement in reviewing these claims”.

For the last few days, we’ve been putting different diapers on our son. Honestly, I can’t say that his rash has changed at all. Maybe he’s recovering slowly from chemical burns, or maybe he has the same virus that’s hit lots of other toddlers. There is no reliable way for me to know.

That’s why I’m glad that the CPSC and Health Canada are taking a look at the issue. Rather than reacting to mass-hysteria, I assume they will employ scientific methods to establish whether or not these bum rashes are caused by Pampers diapers.

Jeff Orchard is an associate professor of computer science at the University of Waterloo in Ontario, Canada. He has degrees in mathematical nerdism from Waterloo and UBC, and got his PhD in computing science from Simon Fraser University in 2003.
Jeff is 99% atheist, 1% agnostic, and is passionate about teaching critical thinking. One of his research goals is to understand how the brain works (and then use that knowledge to take over the world). He has published academic papers in image processing, and is also an evolution buff.